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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

15987 results found.

  1. EP250812a: Liverpool Telescope upper limits
  2. EP250812a: SVOM/VT optical counterpart
  3. GRB 250812A: EP-FXT counterpart detection
  4. EP 250812a: GOTO optical upper limit
  5. GRB 250812A: Kilonova-Catcher optical afterglow detection
  6. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  7. GRB 250812A: SVOM/VT optical afterglow confirmation
  8. GRB 250812A: TRT likely optical counterpart detection
  9. GRB 250812A: SVOM detection of a faint long burst
  10. GRB 250807B: SVOM/VT optical observation
  11. GRB 250809A: LCOGT Optical Upper Limits
  12. GRB 250808A: VLT X-shooter candidate counterpart
  13. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. GRB 250807A: SVOM/VT optical continued observation
  15. GRB 250808A: SVOM detection of a long burst
  16. GRB 250807B: Kilonova-Catcher optical afterglow detection
  17. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  18. EP250807a: NTT z-band optical upper limit
  19. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  20. GRB 250807A: SVOM/GRM observation
  21. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  22. GRB 250807B: NTT optical observations
  23. EP250807a: EP-WXT detection of a fast X-ray transient
  24. EP 250807.979: GOTO optical upper limit
  25. EP250807a: COLIBRÍ optical upper limit
  26. GRB 250807A: SVOM/VT optical observation
  27. GRB 250807B: Swift detection of a burst with an optical counterpart.
  28. GRB 250805A: Kilonova-Catcher optical upper limits
  29. GRB 250805A: Swift/UVOT Upper Limits
  30. EP250806a: Liverpool telescope optical upper limit
  31. GRB 250807A: Swift detection of a burst with an optical counterpart
  32. EP250802a: EP-FXT follow-up observation
  33. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  34. EP250806a: SVOM /VT optical candidate
  35. GRB 250806A: KAIT optical upper limit
  36. GRB 250806A: SVOM/VT refined analysis
  37. EP250806a: COLIBRÍ optical upper limit
  38. GRB 250806A: Kilonova-Catcher optical upper limits
  39. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. GRB 250806A: SVOM/VT optical upper limit
  41. GRB 250805A: SVOM/VT optical counterpart
  42. GRB 250805A: ESO/VLT observations
  43. GRB 250805A: TRT optical upper limits
  44. GRB 250804B: SVOM/GRM observation of a short burst
  45. EP250730a: SVOM/VT optical upper limit
  46. EP250802a: Liverpool Telescope optical upper limits
  47. EP250802a: GROWTH-India Telescope optical upper limit
  48. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  49. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  50. EP250711a: CrAO and Assy optical observations
  51. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  52. EP250730a: COLIBRÍ optical upper limit
  53. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  54. GRB 250725A: PRIME near-infrared observations
  55. GRB 250728A: COLIBRÍ optical upper limit
  56. GRB 250727A: AST3-2 Upper limit
  57. GRB250727A: SVOM/VT optical upper limit
  58. GRB 250725A: SVOM/GRM observation
  59. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  60. GRB 250725A: Swift/UVOT Upper Limits
  61. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  62. GRB 250725A: BOOTES-7 early optical detection
  63. GRB 250725A: SVOM/VT optical candidate
  64. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  65. Swift GRB 250725A: Global MASTER-Net OT detection
  66. SVOM J195836+32283/sb25072103: Second VT observation
  67. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  68. GRB 250717B: SVOM/GRM observation
  69. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  70. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  71. GRB 250717B: COLIBRÍ optical upper limit
  72. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  73. GRB 270713A: Kitab and AbAO Optical Observations
  74. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  75. GRB 250716A: GOTO tentative optical counterpart candidate
  76. GRB 250714A: SVOM/GRM observation
  77. GRB 250713A: Mephisto optical upper limits
  78. GRB 250713A: SVOM/VT optical upper limit
  79. GRB 250713A: NOT optical upper limits
  80. GRB 250706B/C: 7DT Follow-up Observations
  81. EP250711a: COLIBRÍ continuous optical observations
  82. GRB 250713A: JinShan optical upper limits
  83. GRB 250711A: DDOTI Optical Upper Limit
  84. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  85. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  86. GRB 250711A: SVOM/GRM observation
  87. EP250711a: NOT optical counterpart candidate
  88. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  89. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  90. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  91. EP/WXT 01709181970: GOTO observations confirm stellar variability
  92. EP250704a/GRB 250704B: 10 GHz VLA detection
  93. IceCube-250706A: No Candidates from WINTER
  94. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  95. GRB 250704B / EP250704a: VLA radio detection
  96. EP250704a/GRB250704B : HCT optical and NIR upper limits
  97. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  98. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  99. GRB 250702F: radio detection with the VLA
  100. GRB 250706B/C: VLT/X-shooter redshift z = 0.942

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